In the early 2000s, ultra-wideband (UWB) was cited as a promising technology as “wireless universal serial bus (USB).” However, the market turned in a different direction. Nonetheless, the groundwork from the Federal Communications Commission (FCC) was laid so that devices could operate legally in the United States and abroad. Until recently, UWB devices operating in the 3.1 to 10 GHz range tended to be composed of discrete components having a relatively high price point. Recently, however, UWB integrated circuit (IC) chips have come into the marketplace allowing for lower cost UWB transceivers to be built and sold. With the lower price point, these devices may reach a broader audience with greater manufacturing quantities.
Inherent in UWB technology is the ability to create narrow pulse widths. These pulse widths can be used to establish an arrival time of a radio frequency (RF) signal with very high granularity. A precise timestamp can be determined for receiving a signal and transmitting a signal. When timestamps are compared for a message that is sent from one device to the next, a distance between devices can be calculated based on the difference in time and the speed of the signal through the air (Time-difference-of-Arrival or TDOA).
For determining location using TDOA, the devices typically need to be synchronized to a master clock. Crystal oscillators are used in a wide variety of electronics and can serve as a precision clock in ultra-wideband (UWB) applications/electronics. The crystal oscillator may serve as the critical timing element for determining a precise frequency of transmitted messages and for sampling incoming radio frequency (RF) messages.
Crystal oscillators generally have limited tolerances and can typically range in accuracy from about 5.0 to 40 parts per million (ppm). In UWB applications, depending on data rate and carrier frequency, the clock generally needs to have tolerances of less than about 10.0 parts per million (ppm) or greater for reliable communication. Furthermore, temperature may also play a role with crystals deviating from their nominal frequency. If the temperature is too high or too low from relative to room temperature, the frequency of the crystal may deviate.